John,
A lot of the suitability would have to do with how old the gun is and how the floating pins are held in the action. Do they have screw-in bushings behind them or do they have holding screws that hold them in by coming in from the side into a knotch in the pin itself? The ones with the retaining screws tend to wear and if you are not careful,to blow out. I would think that a rifled 20 gauge would be fine, but here again, the overall condition of the gun is all important when trying to contain any extra pressure. I hate to appear ignorant, but I'm not familiar with this model of gun at all. Can you tell us more about it? Maybe send some closeup pictures? Bob H.